1. Priority Information
This application claims priority from European Patent Application No. 03077540.7, filed Aug. 11, 2003, and European Patent Application No. 03076923.6, filed Jun. 13, 2003, herein incorporated by reference in their entirety.
2. Field of the Invention
The present invention relates to a supporting device, a lithographic apparatus, a device manufacturing method, and a position control system.
3. Description of the Related Art
Lithographic projection apparatuses can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, patterning device of the lithographic projection apparatus may generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising one or more dies) on a substrate (silicon wafer) that has been coated with a layer of radiation-sensitive material (resist).
In general, a single wafer will contain a whole network of adjacent target portions that are successively irradiated via the projection system, one at a time. More information with regard to lithographic projection apparatuses as here described can be gleaned, for example, from U.S. Pat. No. 6,046,792, incorporated herein by reference.
In a manufacturing process using a lithographic apparatus, a pattern (e.g. in a mask) is imaged onto a substrate that is at least partially covered by a layer of radiation-sensitive material (resist). Prior to this imaging step, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures, such as a post-exposure bake (PEB), development, a hard bake and measurement/inspection of the imaged features. This array of procedures is used as a basis to pattern an individual layer of a device, e.g. an IC. Such a patterned layer may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., all intended to finish off an individual layer.
If several layers are required, then the whole procedure, or a variant thereof, will have to be repeated for each new layer. Eventually, an array of devices will be present on the substrate (wafer). These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc. Further information regarding such processes can be obtained, for example, from the book “Microchip Fabrication: A Practical Guide to Semiconductor Processing”, Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN 0-07-067250-4, incorporated herein by reference.
In a manufacturing process using a lithographic apparatus, the pattern has to be imaged on the substrate very accurately. Current lithographic apparatuses are commonly used to manufacture devices with typical dimensions in the micron or submicron range. Hence, the pattern has to be imaged on the substrate with a corresponding accuracy. Disturbances, such as mechanical vibrations or air pressure waves, can alter the position of the pattern with respect to the substrate and thereby affect the process. The disturbances may be caused, for example, by floor vibrations, reaction forces of a positioning device of the substrate holder, reaction forces of a further positioning device by means of which the mask holder is displaceable relative to a focusing unit or otherwise. Hence, the lithographic apparatus has to be configured such that disturbances are suppressed or circumvented.
As disclosed in International Patent Application WO-A-96/38766 and U.S. Pat. No. 6,226,075, lithographic apparatuses that are supported by a base via three supporting devices are known. Such supporting devices prevent, inter alia, the transmission of vibrations from the base to the frame. The three supporting devices each have a gas spring positioned between a first part, which is connected to the base,, and a second part, which is connected to the frame. The mass-spring system formed by the known supporting devices and the frame together with the components of the lithographic apparatus supported thereby has a low natural frequency to prevent transmission of vibrations from the base to the frame as much as possible.